With advantages such as easy maintenance, high bandwidth, and low cost, the PON plays a leading role in optical access technologies, and is an ideal physical platform comprehensively integrating access of multiple services such as voice, data, and video through a single platform. The PON technology is a Point to Multipoint (P2MP) optical fiber access technology. The PON is formed by an Optical Line Terminal (OLT), an Optical Network Unit (ONU), and an Optical Distribution Network (ODN). The Gigabit-Capable Passive Optical Network (GPON) technology is an important technology branch in the PON family. The GPON supports a Triple-play service and has a full-service access capability, so that the deployment of services is more flexible. The GPON supports high-bandwidth transmission and long-distance access. The GPON has flexible bandwidth allocation, and has perfect maintenance and management capability to ensure the Quality of Service (QoS). The GPON technology is one of the optical access technologies under the greatest concern at present, and will still be the focus in the following 2 to 3 years.
It is stipulated in a PON system that, the direction that data is transmitted from the OLT to the ONU is a downstream direction, and the direction that data transmitted from the ONU to the OLT is an upstream direction. A GPON system adopts a Wavelength Division Multiplexing (WDM) technology to implement single-fiber bi-directional transmission. In order to separate signals of upstream and downstream directions of multiple users in one optical fiber, a downstream data stream adopts a broadcast technology, and an upstream data stream adopts a Time Division Multiple Access (TDMA) technology. In practical network deployment, for scenarios with a longer transmission distance or more users, a Reach Extender (RE) or a similar device needs to be added between the OLT and the ODN, so as to extend a transmission distance from the OLT to an optical splitter/coupler, or increase a branch ratio of the optical splitter/coupler. Upstream data is sent from the ONU to the OLT in a TDMA manner. Each upstream data block sent by the ONU is referred to as a burst, that is, data is sent in the form of burst data packets. As the burst data sent by each ONU is not precisely synchronized in time sequence, and a bit synchronization error exits, a protection time slot of a certain length is maintained between the bursts to avoid collision. Meanwhile, due to particularity of the time sequence of each burst, that is, the bursts are not in complete bit synchronization, a burst receiver needs to perform bit synchronization each time a burst is received. However, before these steps are performed, the burst receiver generally needs to be reset. An Embedded Optical Network Termination for management of the extender (EONT) in the prior art needs to unpack the downstream data to obtain bandwidth allocation information. To unpack and resolve the downstream data is a relatively complex process, which increases the complexity of the implementation of the RE.